1. Technical Field
The present invention relates to an ink set and a liquid droplet discharging apparatus having the same.
2. Related Art
In the related art, various colored images are formed on recording media using color inks such as cyan ink, magenta ink, yellow ink, and black ink. In recent years, inks which are able to form color images which are not able to be expressed simply by using these color inks have attracted attention. For example, JP-A-2008-174712 discloses forming a photoluminescent image using a photoluminescent ink composition which contains a photoluminescent pigment (for example, gold dust or silver dust made from brass, aluminum fine particles, or the like). In photoluminescent images, it is possible to express photoluminescence which is generated by the luster of metals or the like by using photoluminescent pigments such as metal pigments. In addition, JP-A-6-322306 discloses a white ink composition which contains a white coloring material such as titanium dioxide. This white ink composition is able to form a white image which it is not possible to form with the color inks described above.
Here, when the white coloring material represented by titanium dioxide described above does not have a particle diameter with a certain size (for example, approximately 200 nm or more), there are often cases where the whiteness of the image to be recorded feels insufficient. Therefore, it is necessary to increase the size of the particle diameter of the white coloring material; however, there are problems in that, along with the increase in the particle diameter of the white coloring material, the particles settle in the ink composition. With respect to this problem, for example, JP-A-2007-211176 and Japanese Patent No. 4958001 describe using porous titanium dioxide particles as the white coloring material. It is disclosed that, by using such a porous white coloring material, it is possible to lower the specific gravity compared to the white coloring material using the titanium dioxide of the related art.
However, even in a case where the porous titanium dioxide particles described above are used as the white coloring material, it may not be said that the problem of sedimentation is sufficiently solved and there is still the same problem in that the white coloring material settles. In the same manner, since the specific gravity of the photoluminescent pigments described above is higher than the color pigments of the related art, there is a problem in that it is easy for settling to occur in the ink composition.
When the coloring material which is included in the ink settles, not only does the image quality of the image to be recorded decrease, but defects may occur such as the flow path of the apparatus (for example, an ink jet recording apparatus) for discharging the coloring material becoming clogged, or the discharge nozzles becoming clogged.